FAVIMAT+ test section

Single fibre tensile testing is a fundamental method for characterizing the mechanical properties of textile fibres, reinforcement fibres and filament materials. Standards such as ASTM D3822 and ISO 5079 describe procedures for measuring tensile force and elongation of individual fibres.

However, the most relevant parameter for fibre performance is typically tenacity rather than breaking force. Tenacity expresses the tensile strength of a fibre normalized to its linear density (for example in cN/tex or gpd). Since individual fibres within a sample can differ significantly in linear density, accurate determination of tenacity requires measuring the linear density of each individual fibre.

Conventional single-fibre tensile testers measure only the breaking force, meaning that tenacity is typically calculated using average fibre fineness values. This introduces considerable uncertainty to the tenacity measurement.

The FAVIMAT+ solves this problem by combining single fibre tensile testing with vibroscopic linear density measurement in one integrated system. The linear density of each individual fibre is determined using the vibroscopic resonance method prior to tensile testing. Because both measurements are performed on the exact same fibre segment, the FAVIMAT+ enables precise determination of true fibre tenacity and even stress–strain behaviour for every tested filament.

Single Fibre Tensile Testing According to International Standards

Single fibre tensile testing is commonly performed according to internationally recognized standards including ASTM D3822 or ISO 5079. These standards specify procedures for determining the breaking force and elongation of individual fibres. For reinforcement fibres testing procedures are often defined in more specialized standards, for instance ISO 11566 or ASTM C1557-20 for carbon fibres and ISO 19630 for ceramic fibres.

While these standards define tensile testing procedures, they do not necessarily ensure accurate determination of tenacity, because linear density is often determined separately or averaged across multiple fibres.

Why Accurate Tenacity Measurement Requires Individual Fibre Linear Density

In many conventional single filament tensile tests, only the breaking force (cN) and elongation are measured. However, the material property used to compare fibre strength is tenacity, which normalizes tensile force by fibre fineness:

Tenacity = Breaking Force / Linear Density

Since fibre fineness varies from filament to filament, using an average linear density introduces considerable variation in the test results.  Accurate and efficient fibre characterization therefore requires determination of linear density for each individual fibre prior to tensile testing.

Vibroscopic Determination of Linear Density of Individual Fibres

The FAVIMAT+ integrates linear density measurement using the vibroscopic method according to ISO 1973.  In this measurement principle, the fibre is tensioned between two clamps, the fibre is excited into transverse vibration and from the resulting resonance frequency the linear density (e.g. in dtex or denier) of the individual fibre is calculated.

Compared to gravimetric or bundle-based measurements, vibroscopic determination offers several advantages:

• direct measurement of individual fibres rather than averaged values,
• very high sensitivity also for fine filaments,
• the linear density is measured on the same section of the fibre where also the  tensile test is performed.

Integrated Single Fibre Tensile Testing with FAVIMAT+

The FAVIMAT+ combines vibroscopic linear density measurement and tensile testing within one integrated test sequence.

First, the linear density of the individual fibre is determined using the vibroscopic method. The same fibre is then subjected to a tensile test to determine the force/elongation curve. Because both measurements are carried out on the same fibre segment, the instrument calculates the tenacity/elongation data resulting in a highly accurate measurement of the fibre tenacity in cN/tex. Likewise, also other typical tensile properties are determined such as elongation at break and modulus. If the fibre density (g/cm^³) is know, FAVIMAT+ also calculates the cross-sectional area of the fibre such that also the corresponding stress/strain and modulus values are derived in MPa or GPa. This is particularly useful when testing reinforcement fibres, such as carbon, glass, basalt or ceramic fibres.

This integrated measurement concept eliminates uncertainties associated with average fibre fineness and provides highly accurate mechanical characterization at the single fibre level.

Direct Fibre Clamping Instead of Paper Frames or Tabs

In many conventional single fibre tensile testing procedures, fibres are first mounted on paper frames or in tabs before testing. These are then placed into the grips of a tensile testing machine, and paper frames even need to be cut before the test.

This significantly increases the time required for testing. Preparing and handling paper frames is labour-intensive and limits the achievable testing throughput.

The FAVIMAT+ uses a different approach. The instrument has been specifically designed for handling individual fibres directly, allowing fibres to be clamped directly and reproducibly without the use of paper frames.

As a result, the overall testing process becomes significantly faster. While operators using conventional tensile testers may still be preparing paper frames, the FAVIMAT+ will typically have already completed the measurement.

Additional Single Fibre Test Methods

Beyond tensile testing, the FAVIMAT+ can determine several additional fibre properties. These optional modules allow comprehensive mechanical and physical characterization of fibres at the individual filament level.

Mechanical crimp behaviour of fibres:

The instrument determines key parameters describing mechanical crimp properties, including:

• crimp elongation,
• crimp removal force,
• crimp stability.

These parameters are particularly relevant for understanding fibre behaviour in yarn spinning and non-woven production.

Geometrical crimp structure of fibres:

In addition to mechanical crimp properties, the FAVIMAT+ evaluates the geometrical crimp structure of fibres, including:

• number of crimp bows,
• crimp amplitude.

These measurements provide valuable insight into fibre morphology and processing behaviour.

Bending stiffness of fibres:

Using controlled axial compression of the fibre, the system determines bending stiffness. This property is important for evaluating fibre flexibility and its influence on processing behaviour.

Fibre-to-metal friction measurement:

The FAVIMAT can measure friction between a fibre and a metal surface. This parameter is highly relevant for:

• fibre transport in spinning machines,
• evaluation of spin finishes and sizings,
• analysis of friction behaviour in textile machinery.

Electrical resistance measurement during tensile testing:

For conductive or functional fibres as they are used for instance in smart textiles, the instrument can determine electrical resistance during tensile loading. This allows investigation of the relationship between mechanical deformation and electrical conductivity.

Wet tensile testing of fibres:

The system can also perform tensile testing in liquid environments, such as water. This enables investigation of fibre properties under conditions relevant to textile processing or end-use applications and is commonly tested on cellulose fibres such as viscose or lyocell.

Automated High-Throughput Single Fibre Testing with (AI)ROBOT2

Depending on the applied testing method, single fibre testing can be a time-intensive process. To significantly increase efficiency, the FAVIMAT+ can be equipped with the ROBOT2 and AIROBOT2 automatic fibre feeding systems.

(AI)ROBOT2 enables automated handling of fibre samples and performs:

• automatic fibre pick-up from sample magazines,
• automated positioning and clamping of fibres,
• sequential execution of measurement cycles.

This automation allows high-throughput unattended testing of large fibre series with minimal operator intervention, reducing labour time by up to 95 percent. This increased testing productivity is especially useful in fibre production control.

Applications of Single Filament Testing

The FAVIMAT+ is widely used for precise characterization of individual fibres across many application areas.

Textile fibres and technical fibres testing:

• synthetic fibres such as fibres made from PP, PA, PLA, PES, PSF, PAN etc.,
• natural fibres including cotton, hemp, flax, wool or spider silk,
• high-performance fibres such as UHMPE, aramide,
• and many more.

Single filament testing is essential for reinforcement fibres used in composite materials, including:

• carbon fibres,
• glass fibres,
• basalt fibres,
• ceramic fibres.

FAVIMAT+ is also part of the FIMATEST system to for fibre/matrix-adhesion testing according to ISO 19375 and DIN SPEC 19389.

Conclusion

The FAVIMAT+ significantly extends conventional single fibre tensile testing by enabling accurate tenacity measurement on an individual fibre basis. By integrating vibroscopic linear density determination, tensile testing and additional fibre characterization methods, it provides a comprehensive and precise evaluation of fibre properties.

Combined with the AIROBOT automation module, the system also enables high-throughput testing with dramatically reduced operator effort, making it an ideal solution for laboratories requiring precise, reproducible and efficient single filament testing.

FAVIMAT+ is worldwide the first and only single-fibre tester which combines more than seven test methods in one instrument, for the full characterization of single fibre properties including:

• Linear density, yields denier, dtex and even the cross sectional area of each individual fibre,
• Tensile properties, results in single-fibre strength and tenacity, elongation at break, etc.,
• Mechanical crimp properties, delivers percent crimp, crimp removal force and crimp stability,
• Geometrical crimp structure, determines the number and amplitude of the crimp bows,
• Fibre-to-metal friction, measured precisely on each individual fibre,
• Bending stiffness by axial compression of the fibre,
• Simultaneous measurement of the electrical resistance and conductivity of fibres during the tensile test,
• Fibre/matrix-adhesion testing as key parameter for the performance of composites.